Disposable wipe products have added great convenience as such products are relatively inexpensive, sanitary, quick, and easy to use. Disposal of such products becomes problematic as landfills reach capacity and incineration contributes to urban smog and pollution. Consequently, there is a need for disposable products that can be disposed of without the need for dumping or incineration. One alternative for disposal is to use municipal sewage treatment and private residential septic systems.
Some current non-dispersible wipes are erroneously treated as flushable by the consumer because they typically clear a toilet and drain line of an individual residence. This, however, merely passes the burden of the non-dispersible wipes to the next step in the waste water conveyance and treatment system. The non-dispersible wipes may accumulate, causing a blockage and place a significant stress on the entire wastewater conveyance and treatment system. Municipal wastewater treatment entities around the world have identified non-dispersible wipes as a problem, identifying a need to find options to prevent further stress from being placed on the waste systems.
Numerous attempts have been made to produce flushable and dispersible products that are sufficiently strong enough for their intended purpose, and yet disposable by flushing in conventional toilets. One approach to producing a flushable and dispersible product is to limit the size of the product so that it will readily pass through plumbing without causing obstructions or blockages. However, such products often have high wet strength but fail to disintegrate after flushing in a conventional toilet or while passing through the wastewater conveyance and treatment system. This approach can lead to blockages and place stress on the waste water conveyance and treatment system. This approach to flushability suffers the further disadvantage of being restricted to small sized articles.
One alternative to producing a flushable and dispersible wipe material is taught in U.S. Pat. No. 5,437,908 to Demura. Demura discloses multi-layered structures that are not permanently attached to each other for use as bathroom tissue. These structures are designed to break down when placed in an aqueous system, such as a toilet. However, the disadvantage of these wipes is that they lose strength when placed in any aqueous environment, such as an aqueous-based lotion. Thus, they would readily break down during the converting process into a premoistened wipe or when stored in a tub of pre-moistened wipes.
Another alternative to produce a flushable and dispersible wipe material is the incorporation of water-soluble or redispersible polymeric binders to create a pre-moistened wipe. Technical problems associated with pre-moistened wipes and tissues using such binders include providing sufficient binder in the nonwoven material to provide the necessary dry and wet tensile strength for use in its intended application, while at the same time protecting the dispersible binder from dissolving due to the aqueous environment during storage.
Various solutions in the art include using water soluble binders with a “trigger” component. A trigger can be an additive that interacts with water soluble binders to increase wet tensile strength of the nonwoven web. This allows the nonwoven web, bound with water-soluble binder and a trigger, or with a trigger in a separate location such as in a lotion that is in intimate contact with the wipe, to function in applications such as moist toilet tissue or wet wipes, where the web needs to maintain its integrity under conditions of use. When the dispersible web is placed in excess water, such as a toilet bowl and the subsequent wastewater conveyance and treatment system, the concentration of these triggers is diluted, breaking up the interaction between the binder and trigger and resulting in a loss of wet tensile strength. When the wet tensile strength of the web is diminished, the material can break up under mechanical action found in the toilet and wastewater conveyance and treatment systems and separate into smaller pieces. These smaller pieces can more easily pass through these systems. Some non-limiting examples of triggers include boric acid, boric acid salts, sodium citrate, and sodium sulfate.
The disadvantage of using triggers is that they are only viable in water with certain chemical characteristics. Water that falls outside the viable range for a specific trigger can render it ineffective. For example, some triggers are ion-sensitive and require water with little or no ions present in order to facilitate the trigger mechanism. When wipes using these ion sensitive triggers are placed in water with a higher level of certain ions, such as in hard water, the trigger is rendered ineffective. Hard water is found in toilets, wastewater conveyance, and wastewater treatment systems across North America and Europe and limits where wipes with these types of triggers can effectively be used.
Nonwoven articles using water-sensitive films are also known in the art. However, difficulties have been identified with these articles because many water-sensitive materials like polyvinyl alcohol become dimensionally unstable when exposed to conditions of moderate to high humidity and tend to weaken, stretch, or even breakdown completely when the wipe is pre-moistened, for example a moist toilet tissue or baby wipe. Such materials can stretch out of shape and/or weaken to the point of tearing during use. While increasing film thickness adds stability, it also results in an unacceptable cost and renders disposal difficult. Articles made of thicker films have a greater tendency to remain intact on flushing and clog toilets or downstream systems.
Thus, there remains a need for a wipe material that is strong enough for its intended use, and yet be easily disposed of in an existing toilet and subsequent wastewater conveyance and treatment system. There is also the need for a flushable wipe material with the desired degree of softness for use on skin that can be prepared in an economical manner. The disclosed subject matter addresses these needs.